Preparation and characterization of cross-linked waterborne acrylic /PTFE composite coating with good hydrophobicity and anticorrosion properties

Abstract

The use of waterborne acrylic coatings in anticorrosion applications is challenging owing to the existence of numerous hydrophilic carboxyl groups. Hence, the objective of this study was to develop a facile method of preparing waterborne acrylic anticorrosive coating. Specifically, a waterborne hydrophobic acrylic resin (PFSA) with 3-(methacryloyloxy)propyltris(trimethylsilyloxy) silane (M3T) and 2-(perfluorooctyl)ethyl methacrylate (FMA) as hydrophobic monomers was synthesised via semi-continuous seed emulsion polymerisation. Owing to the substantial influence of the acrylic acid (AA) content on the polymerisation stability, the effect of the AA amount on the emulsion polymerisation process and surface properties of the PFSA film were assessed, where the M3T/FMA mass ratio was set to 4.47. The latex particles were proven to have a core-shell structure using transmission electron microscopy. When the AA content was 2.75 wt%, the water contact angle of the obtained PFSA-2 film reached 103.2°, and the emulsion coagulum was only 0.66%. Thereafter, CPFSA coatings (namely, CPFSA-1, CPFSA-2, and CPFSA-3) were obtained by mixing PFSA-2 with different proportions of trimethylolpropane-tris-(β-N-aziridinyl) propionate (XR-100; 2, 4, and 6 wt%). Similarly, CPFSA@PTFE coatings (namely, CPFSA-1 @PTFE, CPFSA-2 @PTFE and CPFSA-3 @PTFE) were prepared by mixing CPFSA with 2 wt% polytetrafluoroethylene (PTFE). The cross-linking between PFSA and XR-100 reduced the water absorption rate and strengthened the coating hardness, adhesion, and compactness, despite a slight decrease in thermal stability. The addition of PTFE to the CPFSA further improved the film hydrophobicity, smoothness and they all exhibited excellent mechanical durability. Most importantly, electrochemical impedance spectroscopy indicated that the corrosion resistances of the investigated coatings used as the topcoats in 3.5 wt% NaCl solution followed the order CPFSA@PTFE > CPFSA > PFSA-2 > Bare epoxy. Especially for the CPFSA-2 @PTFE coating, |Z| 0.01 Hz was 2.182 × 1010 Ω cm−2 even after 15 days of immersion.